I have had this before. The doctor said it was because of excessive dieting and lack of nutrition. At first, it was only delayed for a few days, then it didn't come for a few months, and then it began to eat well. If your period doesn't come, you will get old, so it's best to go on a light diet to lose weight and exercise.

Dieting can eat more crude fiber food, otherwise you will be hungry, and suddenly eating too much stomach will be unbearable.